1. Field of the Invention
This invention relates to the transmission of communication signals over the AC power line. More particularly, this invention relates to the sensing and matching of the impedance of the power line to maximize signal power transfer while minimizing the radiated power.
2. Description of the Related Art
A variety of techniques have been proposed to address the problem of the variability of power line impedance in communications systems. Generally these techniques use power-conditioning circuits to attempt to adjust the power characteristics to specific desired values. The approach of this invention is to sense the impedance of the power line and to actively adjust the transmitter and receiver connected to the power line to match the power line impedance.
For general background material the reader is directed to the following U.S. patents each of which is incorporated in its entirety for the material contained therein.
U.S. Pat. No. 3,810,096 describes a method and system for transmitting data and indicating room status that has a transmitter and a receiver utilizing the neutral and ground lines of a conventional AC room power line as a communications link.
U.S. Pat. No. 5,349,644 describes a distributed artificial intelligence data acquisition and equipment control system that uses an AC power line to form a local area network.
U.S. Pat. No. 5,869,909 describes a ground voltage reduction device that is connected between a neutral reference node and a ground node defined by two bypass capacitors of a blocking circuit.
U.S. Pat. No. 5,949,327 describes an overhead balanced power distribution network that is coupled to telecommunications signals.
It is desirable to provide a method and system for the determination and matching of power line impedance, which such power line is used as a communication channel. Moreover, it is desirable to provide a method and system that provides maximum signal power transfer to and from the power line for both transmitting and receiving communication signals. Further it is desirable to provide a method and system that minimizes the signal power radiated off the power line and minimizes the reflection coefficient of the power line.
Therefore, it is the general object of this invention to provide a method and system for determining the impedance of a power line which is being used as a communication channel.
It is also an object of this invention to provide a method and system for matching the output impedance of the signal transmitter to the power line impedance.
It is a further object of this invention to provide a method and system for matching the input impedance of a receiver to the power line impedance.
Another object of this invention to match input and output impedance of the receiver and the transmitter to the power line as frequently or infrequently as required.
These and other objects of this invention are achieved by the method and system herein described and are readily apparent to those of ordinary skill in the art upon careful review of the following drawings, detailed description and claims.